Silicon-on-insulator (SOI) integrated circuits include a substrate of an insulating material, such as sapphire, spinel, beryllium oxide or the like, having islands of single crystalline silicon on a surface thereof. Each of the silicon islands contains an electrical component, such as a metal-oxide-silicon (MOS) field-effect transistor, and the electrical components are connected by lines of a conductive material, such as conductive polycrystalline silicon, which extend between the islands over the surface of the substrate. When a SOI integrated circuit containing MOS transistors encounters a pulse of high dose rate transient radiation, electron-hole pairs are generated in the substrate. The fringing field between the source and drain of an off MOS transistor collects these pairs and photocurrent will flow. Photocurrent will also flow between any two silicon lines (polycrystalline or single crystalline) which are at different potentials. This photocurrent flow is a major problem in many types of integrated circuits. Therefore, it would be desirable to have a SOI integrated circuit which includes means for blocking the flow of any photocurrent generated in the substrate.